Figure 6.

In vitro differentiated CD8⁺ T cells suppressed the proliferation of naïve CD4⁺ T cells. (a) The CD8⁺ T cells cultured with SK-OV-3 suppressed naïve CD4⁺ T-cell proliferation in a dose-dependent manner with the stimulation by anti-CD3 mAb. Conversely, the CD8⁺ T cells cultured alone did not have the suppressive activity. The proliferative response was determined by [³H] thymidine uptake. (b) Soluble factors were partially required for the CD8⁺ T cells cultured with SK-OV-3 to exert their suppressive effects. In the transwell system, equal numbers of naïve CD4⁺ T cells were cultured in the outer wells, and the CD8⁺ T cells cultured with/without SK-OV-3 were cultured in the inner wells. (c) The suppressive effect of the CD8⁺ T cells cultured with SK-OV-3 could be partially blocked with the use of neutralizing anti-TGF-β1 and IFN-γ mAbs, while the blockade of TNF-α and IL-2 did not affect the suppressive ability of the CD8⁺ T cells cultured with SK-OV-3. C.P.M. is an abbreviation for counts per minute. The data are presented as the mean ± SEM of three independent experiments. *P < 0.05.